The present invention is described in terms of an igniter assembly and method for igniting a pyrotechnic propellant and more particularly to an air bag inflator system for releasing gas at impact moment to timely inflate a personnel protective air bag, but its utilitity is not limited to that application.
A large number of air bag igniter devices of various types have been employed in the automobile industry to be capable in a matte of milliseconds to convert electrical energy into chemical energy rapidly to inflate protective air bags. These past devises for the most part have included comparatively complex, but not always satisfactory mechanisms to avoid premature and undesirable ignition. An early igniter assembly device, concerned with inadvertent energy releases is disclosed in U.S. Pat. No. 3,971,320, to J. T. M. Lee issued on Jul. 27, 1976, which employs a grounding shunt form a coaxial lead to the housing of an igniter to avoid against accidental firing. Such accidental firings, which can be brought about by changes in outside factors such as an electrostatic charge or radiant or electromagnetic energy or radio frequencies, could result in great harm to persons during the manufacturing process of ignitors or those otherwise meant to be protected by air bag equipment. To further insure against accidental firing, other comparatively complex, expensive and not always satisfactory arrangements have been employed. In this regard attention is directed to the two European patent publications: No. 0658739A2, inventor J. H. Evans, published on Jun. 21, 1995, which teaches an electrostatic spark gap discharge arrangement for two spaced electrodes outside a pyrotechnic cup on one side of a glass-to-metal seal with a bridge wire on the other side of the seal in intimate communication with a secondary pyrotechnic, and No. 745519A1, inventor, D. D. Hansen, published Dec. 9, 1996, which teaches a metal oxide varistor made of pressed powder for protecting the igniter from premature ignitions.
For the most part, past protective devices for preventing premature ignition of igniter assemblies have been comparatively complex in manufacture and assembly, expensive and not always efficient in operation, requiring comparatively complex manufacturing steps and additional parts in assembly.
The present invention provides a new and useful arrangement which is straightforward, and economical in manufacture and assembly, requiring a comparative minimum of parts and space and which optimizes the use of several parts which are also required for normal ignition performance, at the same time, avoiding inadvertent energy discharges often brought about in the past by electrostatic charges created by outside factors.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.